Nitidulid beetles infesting California dates

Four predominant species of nitidulid beetles infest dates in the Coachella Valley—Carpophilus dimidiatus (Fabricius), C. hemipterus (Linnaeus), Haptoncus luteolus (Erichson), and Urophorus humeralis (Fabricius). From 1947 to 1951 inclusive, it was found that during the season dates ripen 75 to 90 per cent of the insects present in dates examined were C. dimidiatus, C. hemipterus being second most abundant. Catches by traps baited with fermenting dried peaches from March to July inclusive were predominantly C. dimidiatus, while H. luteolus ranked second.

To develop from egg to adult at 80° F, it required:

11.9 days for Haptoncus luteolus;

15.8 days for Carpophilus hemipterus;

20.6 days for Urophorus humeralis;

20.7 days for C. dimidiatus.

At 90° F it required:

9.6 days for H. luteolus;

12.4 days for C. hemipterus;

14.7 days for C. dimidiatus;

16.5 days for U. humeralis.

It required a longer exposure to kill the larvae of Urophorus humeralis, at 109° and 115° F at 10, 50, and 90 per cent relative humidities, than it did to kill the adults of Carpophilus hemipterus, C. dimidiatus, and U. humeralis. At 120° F this trend was not apparent. Of the adults, U. humeralis was the most susceptible to exposure to high temperatures regardless of humidity. At 109° F it required a longer exposure to kill the adults of C. hemipterus, C. dimidiatus, U. humeralis, and larvae of U. humeralis at 90 per cent relative humidity than it did at 10 per cent. At 120° F the reverse was true.

Ethylene chlorobromide and ethylene dibromide appear to be more effective than methyl bromide as fumigants of eggs of Urophorus humeralis. Under similar conditions it required six times as much methyl bromide as ethylene dibromide or ethylene chlorobromide to kill 100 per cent of U. humeralis eggs. Ethylene dibromide proved a more effective fumigant against nitidulid larvae than either ethylene chlorobromide or methyl bromide. Ethylene dibromide is as effective to adults of all four species as ethylene chlorobromide or methyl bromide, or even more so. It required a longer period after fumigation with ethylene chlorobromide and ethylene dibromide for the insects to die than with methyl bromide. Seven days after treatment, dates still contained 80 to 85 per cent of the total bromide initially absorbed from methyl bromide fumigation, 44 to 54 per cent of that from ethylene dibromide fumigation.

In laboratory and field experiments it was found that lindane, chlordane, aldrin, dieldrin, heptachlor, parathion, and malathon not only had high initial toxicity to the various species but also an effective residual toxicity. Chlordane and lindane applied as dusts occasionally imparted an off-flavor to dates. Extensive field experiments indicate that a 5 per cent malathon dust applied 3 to 4 weeks before picking is very effective in reducing live beetles and infested dates in the bunch.

Benzene hexachloride, dieldrin, and chlordane, at rates of 1½ to 2 pounds per acre dusted onto the surface of the soil and raked in, prevented a high percentage of the beetles from emerging from the treated soil. Indications are that some of these soil treatments may remain effective as long as 1 to 2 months under Coachella Valley conditions.